A cam follower of this type is described in DE 42 02 507 A1. In this document, a bucket tappet with a cup-shaped piston and a valve-side piston is presented, between which a pressure space is bounded as a component of a hydraulic force transmission device. A lifting stroke of a cam acting on the bucket tappet is varied by the transmission of the movement by the bucket tappet to a gas-exchange valve of the internal combustion engine, such that the pressure space can be changed in its length as a function of the operating parameters of the internal combustion engine. In the mentioned document, this is realized in that a slide controlled by a control pressure as a function of these operating parameters closes or opens a connection of the pressure space to the bucket tappet surroundings. Consequently, the movement of the cam should be transmitted completely to the gas-exchange valve for the case that the pressure space is sealed by the slide. Otherwise, a lifting stroke starting from the cam can be reduced, such that a relative movement relative to the valve-side piston is enabled for the cup-shaped piston, in that when the slide is open, hydraulic medium can escape out of the pressure space into the bucket tappet surroundings.
Although this arrangement allows a continuous variation of the transmission of the lifting stroke from the cam to the gas-exchange valve up to its complete switch-off with comparatively simple means, its reduction to practice depends on, in particular, how much the need for essential freedom from vibrations in the valve train can be brought into line with the achievable stiffness of the hydraulic force transmission device. In addition to the existence of air or gas bubbles, which is, for the most part, unavoidable, the disadvantage for the hydraulic stiffness is a pressure space with a large volume for a comparatively small pressure transmission area. This ratio relevant for the stiffness is unfavorable in the cited document to the extent that the slide is arranged at a comparatively large distance to the valve-side piston, so that an additional hydraulic medium channel to the slide is required. However, this hydraulic medium channel does not contribute directly to the force transmission of the hydraulic force transmission device, but instead merely increases the volume of the pressure space by a stiffness-reducing dead space volume.